In Romeo and Juliet, Romeo and Juliet are dead, and their families end their feud as they realize that their hatred has led to the deaths of their children.
When the final book of the Harry Potter series comes to an end, Voldemort has been defeated through Harry's ultimate sacrifice, and although there has been much loss of life, Voldemort is ultimately defeated.
At the end of Return of the Jedi, the emperor has been killed by Darth Vadar, who is Luke's father, and while Darth Vadar has also died, he and Luke were able to reconcile before his death. Luke returns to the planet where his friends are waiting, and they celebrate the end of the empire.
In the Biblical story of Noah and the Flood, the flood waters recede after a period of time, and Noah, his family, and all of the animals are able to exit the ark. The rainbow becomes a symbol that God will not use a flood to destroy the Earth again.